双表
SELECT A. * , B. *
FROM memberdata A LEFT JOIN members B ON A.uid = B.uid
WHERE 1
LIMIT 0 , 30
三表
SELECT * FROM tx1 left join (tx2, tx3) ON (tx1.id=tx2.tid AND tx2.tid=tx3.tid) where tx1.id = 3
双表
SELECT A. * , B. *
FROM memberdata A LEFT JOIN members B ON A.uid = B.uid
WHERE 1
LIMIT 0 , 30
三表
SELECT * FROM tx1 left join (tx2, tx3) ON (tx1.id=tx2.tid AND tx2.tid=tx3.tid) where tx1.id = 3